how do I make to recognize the body of the robot, as blender recognize just the body?
Hint: You can enable Main Menu/Game/Show Physics Visualization. It allows you to see the physics mesh while running the game.



When you use the mesh object as presentation object and as physics object - ensure to select the right Physics/Collision Bounds/Bounds.

When you use one of the primitive collision shapes (box, cylinder ...) the mesh should be symmetrical around the origin. This means the origin should be in the middle of the object. According to your description, this is not your current situation.

Example:



The origin of this mesh is not in the vertical middle. With the primitive shapes the mesh will be out of the bounding box and out of shape:



When you use detailed shapes the origin does not need to be at the middle. But they need much more processing power:



In all cases the origin should be inside the bounding box of the mesh. Otherwise the physics might calculate results you do not expect.